1. Field of the Invention
The present invention relates to a method and apparatus for producing a simple printing plate, especially an ink-soaked printing plate for use as a stamp, a seal, or the like. Particularly, the invention is concerned with a method and apparatus for producing a simple printing plate or an ink-soaked printing plate, using means for bringing a to-be-embossed member, which is a sheet having open cells, into pressure contact under heating with an embossing member having an intaglio plate as a female die to transfer a desired relief image onto the sheet.
2. Description of the Prior Art
Printing plates are being improved day by day, and now resinous relief printing plates, planographic printing plates and intaglio printing plates, which are formed using photosensitive resins, are most popular as a substitute for the conventional metallic printing plates. On the other hand, such simple printing systems as copying machines and ink-soaked printing plates are being utilized not only for office works in companies but also even in homes at large.
Under these circumstances, it is required to provide a system which permits easy fabrication of a printing plate without requiring skill or the use of large-scale equipment. As one of the printing plates which meet such requirements, an ink-soaked printing plate is becoming more and more popular.
The ink-soaked printing plate is a printing plate having a relief image on the surface of a porous material, and by holding ink in the porous material it is possible to effect continuous printing without replenishing ink at every printing. The ink-soaked printing plate is used mainly as a seal or stamp. As the porous material there is usually employed a thermoplastic resin or rubber.
As a method for producing such an ink-soaked printing plate there is disclosed in JP 53-136080A a method wherein a thermoplastic resin powder having fine open cells therein is charged into a female die having a concave portion, followed by hot pressing, to obtain a printing plate for use as an ink-soaked printing plate. In JP 62-16188B there is disclosed a method wherein a masking member having an image is brought into close contact with a material for an ink-soaked printing plate such as rubber or a soft synthetic resin, followed by radiation of a laser beam through the masking member to remove the unmasked surface-layer portion, thereby affording a printing plate for use as an ink-soaked printing plate. In JP 55-90361 A is disclosed a method wherein a pasty material comprising a water-soluble salt powder and a synthetic resin powder is applied to the surface of a substrate to obtain a material for an ink-soaked printing plate, then this material and a die having a relief image are brought into pressure contact with each other under heating to form the relief image on the said material, followed by removal of the die and subsequent washing to remove the water-soluble salt powder, thereby affording a porous printing plate for use as an ink-soaked printing plate.
In JP 3-254982 A is disclosed a method wherein a cylindrical material for an ink-soaked printing plate mounted on a shaft member and having open cells is allowed to roll with respect to a flat embossing member having a relief image to afford a cylindrical printing plate for use as an ink-soaked printing plate.
Thus, conventional printing plates for use as ink-soaked printing plates are produced either by placing a porous material such as rubber or a thermoplastic resin into a die having a relief image and then applying heat and pressure or by fusion-bonding an image-bearing sheet to a porous foam under heating. However, the following problems have been encountered in the above methods:
(1) In the above methods there usually is employed a pressing machine, but a manufacturing process using this machine is inevitably required to be a batch type process, which is unsuitable for mass production and which does not permit continuous fabrication of printing plates. Besides, in the case of using a metallic die, the cost for producing the metallic die is high, PA1 (2) In the conventional manufacturing method wherein both an embossing member and a to-be-embossed member corresponding to a material for an ink-soaked printing plate are contacted and pressed together throughout the respective whole surfaces, it is difficult to apply pressure accurately and uniformly to the whole of the contact portion, so that a difference in a dimensional change of a relief image present between the embossing member and the to-be-embossed member is apt to occur locally, and PA1 (3) In the method disclosed in JP 3-254982 A, since it is necessary to attach the material for an ink-soaked printing plate to a shaft member, this method is not suitable for mass production; besides, since the transfer of a rotating force is done through both the embossing member and the to- be-embossed member, there occur such problems as a positional deviation of the relief image on the resulting printing plate and a dimensional change of the embossing member from the relief image. PA1 an embossing cylinder for holding the embossing member over an arcuate surface; PA1 a to-be-embossed cylinder for holding the to-be-embossed member over an arcuate surface; and PA1 a drive means for rotating the embossing cylinder and the to-be-embossed cylinder synchronously.